One of the more common questions I have received over the years I've been writing Atheist Revolution is which religion I consider to be the worst. I've recognized that those asking it almost always have a particular agenda and rarely one with which I agree. Many are Christians who seem to find great solace in the hope that I'll say something besides Christianity. Some are rabidly anti-Islam and are merely looking for an opportunity to bash Islam or Muslims. Some are atheists who consider any answer other than "all of them are equally bad" objectionable for one reason or another. Despite all of this, I do have some brief thoughts on the question I'd like to share here.
I was raised as a Christian in a predominately Christian region where Christianity was not merely the default but was so pervasive that I was surrounded by people who were largely ignorant of the fact that not every person on Earth was Christian. As I realized I could no longer believe in gods, I was scared. I feared a variety of negative outcomes that might result from letting others know that I was an atheist. I feared that I might be disowned by my family, subjected to discrimination and/or bigotry, or even physically assaulted. But there is one thing I never feared, one thing that never occurred to me in the process of transitioning from Christian to atheist. I never feared that I would be killed for walking away from Christianity.
Had I been raised as a Muslim and lived in an Islamic theocracy like Saudi Arabia, I'm not sure I'd be able to say that. In fact, I suspect that if I had been raised as a Muslim and been living in an Islamic theocracy at the time I'd have been more than a little worried about this possibility. The probability of it happening would have been much higher, and I think that's important to recognize.
Say what you will about Christianity (and I agree that there is plenty to say), but modern Christians have a very different take on ex-Christians than many modern Muslims have on ex-Muslims. Ex-Muslims who grew up in countries where killing apostates was not as rare as it should be are brave in a way I've never had to be. Leaving Christianity behind was hard enough as it was; I can't imagine adding the threat of being murdered on top of everything else.
I am well aware that Christianity has a long history of which no one should be proud and that this includes the murder and torture of "heretics." Islam has a similar history, but there is at least one important difference: too much of this sort of thing is still happening today. So while I do consider all modern religions to be both wrong and detrimental to humanity, I cannot pretend that all are equally harmful when it comes to the most basic human rights.